Polycrystalline diamond (PCD) materials and PCD elements formed therefrom are well known in the art. Conventional PCD is formed by combining diamond grains with a suitable solvent catalyst material and subjecting the diamond grains and solvent catalyst material to processing conditions of extremely high pressure/high temperature (HPHT). During such HPHT processing, the solvent catalyst material promotes desired intercrystalline diamond-to-diamond bonding between the grains, thereby forming a PCD structure. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.
Solvent catalyst materials that are typically used for forming conventional PCD include metals from Group VIII of the Periodic table, with cobalt (Co) being the most common. Conventional PCD can comprise from 85 to 95 percent by volume diamond and a remaining amount of the solvent catalyst material. The solvent catalyst material is present in the microstructure of the resulting PCD material within interstices or interstitial regions that exist between the bonded together diamond grains.
The solvent catalyst material is typically provided during the HPHT process from a substrate that is to be joined together with the resulting PCD body, thereby forming a PCD compact. When subjected to the HPHT process, the solvent catalyst material within the substrate melts and infiltrates into the adjacent diamond grain volume to thereby catalyze the bonding together of the diamond grains.
The HPHT process conventionally used to form PCD is one that involves elevating the temperature and pressure of the diamond grain volume and catalyst material to a desired sintering condition rapidly in a single step. For example, such conventional PCD is formed by subjecting the diamond grain volume and catalyst material in a single step to a temperature of approximately 1,450° C. and a pressure of approximately 5,500 MPa using a cubic press. During this temperature and pressure condition, the solvent catalyst material rapidly melts and infiltrates into the diamond grain volume and catalyzes the intercrystalline bonding together of the diamond grains to form PCD.
A problem known to exist with such conventional PCD materials is that during such single-step HPHT process, one or more constituent materials in the substrate are known to melt and infiltrate into the diamond grain volume so rapidly that that results in the eruption of such one or more constituent materials from the substrate and into the adjacent diamond grain volume. While a known substrate constituent material that undergoes eruption is the catalyst material, other substrate constituent materials such as tungsten carbide can be introduced into the diamond grain volume, e.g., when the substrate comprises tungsten carbide.
Because the sintering temperature exceeds the melting temperature of the solvent catalyst material in the substrate, the rapid escalation of the solvent catalyst material under these conditions causes the solvent catalyst material within the substrate to erupt therefrom and into the diamond grain volume. Such eruption of the catalyst material is known to result in the formation of localized concentrations, regions or columns of the catalyst material or other substrate constituents within the sintered microstructure, in the form of columns that extend vertically from the substrate interface and through the diamond grain volume.
The presence of such columns or localized concentrations of the catalyst material is not desired because: (1) they can reduce the effective amount of the diamond grains that are bonded together during HPHT processing due to the concentrated rather than distributed arrangement of the of the catalyst material within the diamond grain volume: (2) the presence of such densely concentrated regions of catalyst material can impair formation of an uninterrupted polycrystalline diamond matrix, which can reduce the strength and toughness of the PCD material; and (3) such columns or localized concentrated regions of the catalyst material within the PCD material can provide a source of large thermal expansion differences within the microstructure, as the catalyst material is known to have a coefficient of thermal expansion different from that of the surrounding polycrystalline diamond matrix, and the presence of such concentrated regions of catalyst material can thereby operate to reduce the overall thermal stability of the PCD material.
It is, therefore, desired that a polycrystalline ultra-hard material be developed and constructed in a manner that avoids such unwanted substrate material eruption, thereby minimizing or eliminating the presence of such localized concentrated regions or volumes of the catalyst material or other substrate constituents within the resulting sintered product. It is desired that polycrystalline ultra-hard materials developed in this manner have improved properties of toughness, strength and thermal stability when compared to those of conventional PCD comprising such unwanted localized concentrated regions or columns the catalyst material or other substrate constituents caused from catalyst material eruption during sintering as described above.
It is further desired that such polycrystalline ultra-hard materials be engineered to include a suitable substrate to form a compact construction that can be attached to a desired wear and/or cutting device by conventional method such as welding or brazing and the like. It is still further desired that such polycrystalline ultra-hard material and compacts formed therefrom be manufactured at reasonable cost without requiring excessive manufacturing times and without the use of exotic materials or techniques.